Spark plug



im# 259 w49 F. a. MCQARTHY Eli-AL SPARK PLUG Filed oct. 25, 1944 sz 7/ vai.

BY@ WW1# MM ATTORN EY Patented Jan. 25, i949 UNITED ,STATES PATENTOFFICE :SPARK Pima Frederick l. gMcGarthyand Charles Schandler, NeWYork, N.

.Application 0cto`berr23, 19414, .Serial No. 559,880 4 Claims. (Cl.12S-169) This invention relates to .spark plug-s Jand :more particularly.to special means increasing .the Ydis-- sipation of heat from 'the.electrode cap to the parts of the spark plug which-.dissipate Iktheheat.

The immediate object is the ,provision .of means giving the best.possible effrciency `or :heat transfer .with the provision for" meansgiving .the best possible efficiency of eiectrical conduction, without.these functions -con-'Llicting Awith each other, or one diminishing theother.

For this purpose the .invention Yconsists .of a spindle `having .a -corefilled with a compact of compressed silver powder., the boreextendingbeyond .a compact of powdered copper :and silver located .at about 'onehalf .the length 'ci the silver compact the spindle, whereby'the heat:of the electrode :can is quickly transmitted to the copper and silvercompact, .from there to :the iheat dissipators ci the spark plug, 4

Also., the vinvention consists of :a spacer washer in the spark gap to'resist a `closing of fthe. spark gap when V.the copper and `silver.powder is 'being compacted, which Awasher is then 'removed after thespark .plug is completed, .the Washer maintaining the proper dimension.for the :Spaink :gap

and preventing the breaking .of fa porcelain .'sleefve acti-ng .as aninsulator.

The invention will be further described., vrein-v bodiments .thereofshown in `the drawings, land will be 'nally Ipointed out inthe .claims.

"In ithe accompanying drawing-s,

Figure l is a cent-ral vertical section of a Aspariti v plug embodyingthe invention;

Figure 2 is a central vertical section of the irnproved electrodespindle, v'completely lled;

Figure 3 is a central Yvertical section 'of 'the improvedspindle iil'ledabout one third.; Figure '4 is a central vertical section of the im#provedspindle illed about two thirds;

Y Figure `5 vis an .enlarged fragmentary section .of the electrode capand spark gap parts;

Figure 6 is a horizontal vsection 'taken .on line S-S of Figure 5, and

Figure 7 is `a pla-n view o .the `spacing washer. Similar characters orreference indicate .corre-- sponoiing parts throughout .the various-v-iews,

Referring to the drawings, ythe .spark plug` shown in Figure l, has theusual and known :ele-

ments, with the impro-cement vhereinafter .claimed embodied therein.

The improvement consists in moulding they spindle or ste-m i@ rfor theelectrode with a iiore` Ii extending from the electrode can 22.1130 -theother Vend ci the stern, .and '.lling this bore l'l almost throughoutlits entire length tightly' compacted metallic powder, such as silver,having the higihest conductivity ofi heat.' Triispowder -is compactedvery tightly by pressure.andicon-unression, so as to form substantially:a solid '8.

such :a powder -i-s 'flocculent and thus 'takes up a considerable volumebefore its compression to vextent necessary, the present `day method :isto compact it in three stages. :In Figure :is shown the iirst stageindicated .to :height .'shown generally fby fifi. The second stage is.shown in Figure 4, .indicated yby the height shown by 1.5, andrti'eiinal stage is shown in `Eli-gute 2, indicated be' l'hei'.gfht.show-n by l5. 'The compression top `indicated by iii `in Figure -4'disappears when the next stage is added. Likewise, 'the :line t5disappears in Figure These .lines are shown for clarity., though a.merger 'of the achat-ges Xtakes piece. There may Line, howeve a slight'Variation in compactness, the tcp of vone charge tand the adfacentboton of .the next upper charge as ccmpacting oimeta'l .cow-.der dependson forces .applied and their reactions. For practical purposes, theAcharges ci "Figure 2 Iact as one integral Ype'ce. 'I'liecoinpressmn issuch as to 'avoid 'all air spaces in the compr-esseci material Yandbetween it land the walls forming the ieore. 'The compacted inlay is orsilver, and the surrounding hollow lspindle and cap 1-2 -is made ofstainless steel.

Surrounding the spindle 'a closely -iting cylinder Il of insulatingmaterial, preferably mica sheets wound spira'lly around the spindle,which extends the cap 2.2 'or lower xend of the spindle tc the upper endof the same to below a bent over outwardly haring portion of Athe upperYend .of the spindle vas at 9. The cap '212 Ivof the spindle vhas acir-cular recess fm for :the entrance oi the "lower 'end 'of this"insulat- -cyiinder l?. For electrical purposes it is important thatthisinsu-lating cylindrical Lsleeve be firmly sea-'ted recess lf3, 'and'be tightly wound with the edges tightly abutting, to pre Ven-telectrical leakage. 'The recess i8 is Jsuiflciently wide in theembodiment shown, to accommodate also a cylindrical sleeve iis ofvporcela'in -or the like, insulating vmaterial which has its lower endseated the recess w8, and which extends Japin/'alrfll's7 to seat againstshoulder Eil in the exteriorly screWth-rea'ded member Zfi. Thisporcelain sleeve t8 is used as e. see-oer the spark `slug :and asa'protector placed :at the inner end `of 'the ping, to :guard 'theexterior Voiv Ythe mica :cylinder li from spotting. The' Spa-cer actionis new important in olf the following.

'The cap '22 has a plane circumferential sur` face 23, lwhich isparaiilel with -a 4plane circumferential suriacejikoi the member 2l,rand these surf-aces are spaced from each other .to form :a

spark gap 2E.' The member 2i 'has 'a lcirmnmferential recess 26, 4thedepth and iwli'dth o1" 'this recess determining the temperature of -tnecir'- 4v forming a space 36a with the exterior of the insulating sleeveI1, which space is lled with a suitable cement.

' A plurality ofmica washers 38 are piled upon the copper washer 36,which extend upwardly to the upper endof the mica sleeve I1, both ofalignment. The thickness of the disc 21 is slightly larger than or equalto the space oi` the spark gap 25. This disc 21 is made of celfree fromany intervening material. time, the surfaces 23 and 24 are clean.

The washer 21 acts as resistor to the closing of the spark gap, whichhas been found to take place when the metal power is pounded Vandcompacted to the inlay 30. The presence of the washer prevents thisclosing of the gap. Heretofore, a closing of the gap broke the ceramiccylinder 19.. The use of the washer Z1 prevents any compression upon theceramic cylinder i9, if used. Heretofore, the ceramic cylinderdetermined the width of'the spark gap, but now the washer assures theexact width of the spark plug within tolerances.

Above the spark gap region, the member 2| is provided with a shoulder32, which forms the bottom of a conically shaped bore V3| of the.,

member 2l, which bore 3| extends to an upper shoulder Zia. After thespindle with its surrounding mica insulator has been inserted into themember 2|, a conical sleeve 33 of metal is slipped down over the micacovered spindle. Powdered metal, such as a mixture of copper and silveris then charged into the remaining space between the exterior ofthesleeve 33 and' bore 3|. To prevent the powdered metal from beingforced between the shoulder V32 and the bottom lof the sleeve 33, thereis rst inserted a small charge of mica powder and this is tightlystamped and compressed and forced into the space 31. Part oi this may beforced to the lmica sleeve |1, and thus form an eicient protector forthe sleeve and prevent any metal powder from entering the mica sleeveand cause electrical leakage or a short. The mica filled space 31prevents any metal powder from falling between the mica cylinder |1 andthe bore 23a,l

and into the ceramic cylinder and into the spark gap.

The conical shaped sleeve 33 extends upwardly in tapering form to theupper part of the bore` 3|, and the internal bore of which sleeve hugsthe exterior of the insulating sleeve i1. Between the exterior of thesleeve 33, and the bore 3|, the intervening space is nlled with ametallic power such as silver and copper in preferably equalproportions, tightly compacted by pressure to remove all possibility ofair spaces between the particles of the powder and to form a solid ofkthe metal. The metal inlay also preventsv air between it and the wall ofthe bore 3|. VThel sleeve 33 is pressed tightly against the mica sleeve|1 when the copper and silverV is compacted. The sleeve is` preferablyof copper or copper and silver alloy. In place of a tapering sleeve, thesleeve 33 may be of cylindrical shape, as it is largely a protectorforthe exterior of the mica sleeve, which mica cannot resist suicientlythe high compacting pressures applied to the powder. The compacted metal3l] is then capped with a washer 33 of copper or of copper and silveralloy, which has preferably a curved portion,

which are capped by a washer 39 of brass, which has a curved innercontour 4U', over which the v upper end ofthe spindle is bent and outl0lulose acetate, and it may be readily dissolved by a suitable and knownsolvent such'as acetone, and when so dissolved, the spark gap is At thesame v.wardly flared as at 9.

Above the washer 39, is a washer 4I of insulating material, the circularopening of which has a corklike top piece 42 of brass, tting therein.The chamber 43 acts as a spark gapfor the spark passage from the bentend 9 to the top piece 42. The interior of the upper part of the spindleis provided with athinning Ila which forms a shoulder, and whichthinning enables the bending and'flaring to-be carried out as at 9. Theaction of this sparking is described in U. S. -Letters Patent No,2,357,602 of September 5, 1944, issued to Melville F. Peters and Fred I.McCarthy. Y

Within the limitation of electrical conductivity,

' the diiiicult problem is the removal of heat and the prevention ofleakage of gases. Air being a bad conductor of heat, must be removedfrom thev path of heat flow; and the passage of heat from the heatedelectrode cap 22 is the second criterion. To carry out these conceptsthe metal is so compacted as to remove all air pockets, and thecompacting of the metal powders of silver and copper in the bore of themember 2|, brings about reactions of compression between the rathersolid, and therefore pressure resistingwalls of the member 2|, and theexterior of the thin sleeve 33. This is rather thin and the pressure isreadily transmitted to the mica insulating sleeve and to the exterior oftheV spindle |0,1 and through the spindle walls to the inlay 8 ofcompacted silver. This inlay by the high pressures applied is also freefrom air pockets, As the -bore of the spindle i0 is iilled to about thelevel I6', the pressure applied very slightly expands vthe walls ofstainless steel spindle, but not sufcient to interfere with the assemblyof Y Vparts as described and as shown in Figure 1, or

sufficient to provide a wavylike exterior to the spindle.

The foregoing actions have been emphasized to bringout intimate contactsunder forces of pressure, which aid the flow of heat from the silverinlay 8 to the compacted metal 20 and to the member 2| and shell 44,which latter dissipate the heat. The heat flow is subject to Vthe heatresistance of the mica sleeve which is made as thin as possible, yetassuring a proper insulation for the electric conductivity of the sparkplug.

Surrounding the mica washers 38 and the parts just described` is asleeve 45 of mica, which extends from they copper washer 36, and theshoulder Zia, upon which it rests, to the upper most end of the shell 44of the spark plug. A circular recess 44a in the shell 44 seats anangular annulus 46, capping the end of the mica sleeve 45. The shell 44is exteriorly screwthreaded at 41, and has an enlargement of hexagonalshape at 48, and has an exterior screwthreaded portion 49, which engagesinterior screwthreads 50 of the member 2|. The member 2| is providedwith an enlargement 5| of hexagonal shape and has screwthreads 52 toenter the screwthreads of the motor cylinder.

It is important to conduct the heat quickly from the lcap 22 to thelocality of the inlay B. For this purpose, the bore extends down to aslow a part of the interior of the cap as manufac turing conditionspermit. The silver inlay has a quick conductivity of heat and the heatquickly passes to a position in the inlay opposite to the metal compact30, which .being of copper and silver has a quick heat transmissionfactor. The thin stainless 'steel spindle transmits heat quickly in adirection transverse thereto. However, the spindle does not transmitheat longitudinally as quickly as the inlay does. So, the new functionis the quicker transmission of heat within the bore of the stem orspindle, than that of the hollow spindle itself or a spindle made solid.The extension of the inlay above the locality of the compact 30 is toact to'conduct the heat beyond the locality, from which upper part theheat is also withdrawn. Furthermore, the corelationship of`conductivities of heat and electrical current, facilitates the electricflow to the upper end of the spindle in proximity to the positivelead-in conductor at 42.

The electrical conductivity of silver and copper at C., with silver as astandard is 100% for silver, and 99.9% for copper. copper have thesmallest resistance for a given volume. is diminished by an increase intemperature it is important to dispose of the heat, and this is availedof by reason of the from the spindle at the locality of the part 30.

The heat conductivity of the stainless steel spindle is less than thatof the silver. The steel oi the lower shell is preferably of carbonsteel of about 1045, which emits heat quickly.

As is known, the electrical pole of one polarity is connected with thelower shell or member 2l, which by the screwthreads 50 is connectedw-ith the upper shell 44. The pole of opposite polarity is connectedwith piece 42, which is in electrical connection through the sparkingchamber 43, with the spindle lil, and cap 22. These polarities must beseparated in al1 events and electrical leakage prevented, and this iscarried out by the longitudinally extending mica cylinder I7, which isintermediate the spindle Hl and f the parts 2l and 44, augmented by themica cylinder 45 and washers 38.

Gas leakage is prevented by the actions of forces in a lateral, or inrespect to Figure 1 horizontal direction, with the tightly compressedportion of the mica cylinder l1 between compacted metal 30, and thecompacted inlay 8.

Heat transfer is obtained from the heated cap Y 22 immediately to thesilver inlay, to the region or zone of the compacted metal 30, and tothe members 2| and 44, through the laterally thin spindle wall l0,laterally thin mica layer, and laterally thin sleeve 33. Mica is a poorheat conductor, but an excellent electrical insulator, but whatever heatis passed is immediately conducted to the metal 30, the silver andcopper of which provides a quick transfer of heat to the shell.

Spark plugs of the kind shown in Figure 1, have given a very high ratingof 381 (IMEP test).

In the drawings, the silver inlay has been shown to about the line I6,but the inlay may be extended to the shoulder 46a, or above, if theshoulder be raised.

We have described several forms of our invention, but obviously variouschanges may be made in the details disclosed without departing fromSilver and As the electrical conductivity of metals subtraction of heat6 the spirit of the invention as set out in the following claims.

We claim:

l. In a. spark plug, the combination oi an exterior heat dissipatingshell having a central bore and a larger diametered bore concentricthereto,

and having an electrode for one polarity, a spindle extending throughthe central bore of the shell having an. electrode for another polarityat one end, and having a hollow bore extending from the electrode to itsother end, and an insulator between the spindle and the central bore,insuiating the opposite polarities, said electrodes being dis posed atspark gap distance from each other, said larger bore of the shell beinglled with compacted and compressed powder containing silver forming asolid without air spaces and free from air spaces between the solid andthe larger bore and between the solid and the insulator, and a compactof compressed silver powder inthe bore oi the spindle, extending fromits electrode to beyond the compact of the shell bore, whereby a heatexchange action takes place through both compacts from the spindleelectrode to the shell.

2. The structure of claim l, andra washer surrounding the insulator,with a curved inner part above the compacted powder in the shell bore,and an insulating lling between the curved inner part and the insulator.

3. The structure of claim l, and a metallic sleeve interposed betweenthe .metal powder compact in the shell bore and the insulator, and alling of insulating material between the sleeve and the wall of the boreof the larger shell.

4. In a spark plug having an exterior heat dissipating steel shellhaving coxial bores each with a vertical wall, 'one bore having a largerdiameter than the other, said shell having a sparking tip for onepolarity, a spindle extending through the bore of the shell having atone end a sparking tip for another polarity, and an insulator around thespindle between it and the wall of the smaller bore, the diameter of thespindle and its insulator being substantially equal to the diameter oithe smaller bore for insulating `the opposite polarities, the wall ofthe larger bore being spaced from the spindle with its insulator, saidsparking tips being disposed at spark gap distance from each other, aconical metal sleeve having its base rest on the bottom wall of theshell forming the larger bore and having its inner bore diametersubstantially equal to the outer diameter of the insulator, andsurrounding the insulator, and a metal filling between said sleeve andthe vertical wall of the larger bore, the combination of a cylindricalouter wall at the lower end of said sleeve, and a ring of insulatingmaterial between said cylindrical outer wall and the vertical wall ofthe larger bore, and resting on the bottom wall of the shell.

` FREDERICK I. MCCAR'IHY.

CHARLES SCHANDLER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,139,793 Benton Dec. 13, 19382,186,038 Peters Jan. 9, 1940 2,280,972 Paulson Apr. 28, 1942 2,357,602Peters et al Sept. 5, 1944 2,377,481 Christie June 5, 1945

